The present invention relates in general to a conveying or hoist system which is preferably of the programmable type. More particularly, the present invention relates to a conveying or hoist system having an improved control in accordance with the present invention to control certain parameters at one or more stations in the system. The principle parameter being controlled in accordance with the disclosed embodiment is a rectifier.
An automatic conveying system has found extensive use in the field of electroplating. As part of the electroplating process there are tanks at locations in the system having settings associated therewith usually under rectifier control to assure a predetermined thickness of deposit on the piece being electroplated. It is common for the operator of the system to make the rectifier setting dependent upon his knowledge of the particular piece being conveyed. This, of course requires the operator to periodically make the rectifier adjustments at each tank. This also means that an inexperienced operator may quite easily make the improper setting for the electroplating process. Another technique employs a mechanical device on the flight bar of the hoist which may be adjusted by the operator and which activates a receiver on the target tank when the piece enters the tank. This technique has become troublesome because of the corrosive atmosphere associated with the tank so that proper control has not always been provided. Another technique that has been used is the use of computers to make the system essentially entirely programmable. However, this tends to make the system quite expensive and thus not justified from a practical standpoint. This is further complicated by the difficulty with a computer system to account for interruptions in the conveyer system such as a manual interruption of motion of the hoist.
It has also been found more recently that it is desirable to provide a more precise control of the electroplating process or like process. This control is by means of control of the rectifiers which in turn control the amp-hours of power applied in the tank during this plating process.
Accordingly, one object of the present invention is to provide an improved control for a conveying system. The control in accordance with this invention is in particular a control for rectifiers or the like for controlling the plating in an electroplating process so as to control the thickness of plating. Although the principles of the invention are described in connection with rectifier control, it is understood that the principles of the invention may also be used in association with other types of control. For example, the control signal, rather than setting a predetermined rectifier power level, could set a timer for controlling the duration of say a spray step.
Another object of the present invention is to provide an improved control for a programmable conveying or hoisting system of the station searching type.
A further object of the present invention is to provide an improved control system that operates accurately and is not effected by any interruption, or operation of the program not previously programmed.
A further object of the present invention is to provide an improved control system in accordance with this invention that provides precise control and that can be used and operated even by a relatively unskilled operator.
Still another object of the present invention is to provide an improved control system that does not require mechanical switching devices and in particular such devices that must operate directly in the tank environment.